Infinitely variable gear transmission with automatic gear coupling

ABSTRACT

An infinitely variable gear transmission system for vehicles includes a differential gear unit for input, a planetary gear unit, a hydraulic pump and a hydraulic motor, the hydraulic pump rotating with the first output shaft of the differential gear unit and one of the three gear, elements of the planetary gear unit, the hydraulic motor rotating with the second gear element and a control unit to selectively control the fluid pressure in the hydraulic circuit by adjusting the flow control valve, and control the speed of the third gear element in clockwise and anticlockwise direction. In another embodiment the prime mover is directly connected to one of the three gear elements of the planetary gear unit, and also connected to the second gear element through a conventional speed variator and controls the speed of the third gear element by automatically adjusting the speed variator.

This is an addition to my Indian application No: 1439/CHE/2004 for whichpatent has been granted as Patent No: 209664 on 5 Sep. 2007, andinternational application No. PCT/IN2005/000142 published on 26 Jan.2006 for which U.S. Pat. No. 7,632,205 has been granted on 15 Dec. 2009.

TECHNICAL FIELD

The present invention is directed to an infinitely variable geartransmission system for a vehicle drive line and, more particularly, toa transmission system having a single stage planetary gear unit(epicyclic gear unit) coupled with a differential gear unit, and anautomatic gear coupling, with microprocessor control.

BACKGROUND OF THE INVENTION

Current transmission assembly for automatic transmission, a standardaccessory in the modern vehicles, can provide normally 4 or 5 gearratios between the prime mover and the driven wheels for building up thenecessary torque while the vehicle moves from zero speed to the normalspeed, and for over drive. The variable transmission systems currentlyin use, mostly rely upon conventional speed variators, such as steelchain with flexible pulley, toroidal drives, hydraulic torqueconvertors, electric generators etc. for transmitting the power, whichprimarily suffer from the delay for responding to load change, and alsothe limited capacity, and the inability to efficiently transmit thepower, mainly due to the loss suffered by the conversion of mechanicalpower into pressure energy, electrical energy etc. There are also known“torque transfer systems” (Phelan) which can be used only for forwardmovement, in one configuration, and not for reverse and overdrive, whichneeds different configurations of gear elements. These systems can beused only for differential drives and produce excessive heat duringnormal operation wherein one of the hydraulic pumps will dischargeagainst the other hydraulic pump, keeping both the pumps in a lockedposition having no torque differentiation. Additionally, thesetransmission systems are expensive and suffer from operationalinefficiency such as delay for automatically correcting the torque levelfor different driving conditions, resulting in excessive fuelconsumption, poor acceleration, dirty emission and high rate of wear.The automatic transmission system for which an Indian patent and a U.S.patent has been granted to me, as mentioned earlier, eliminates theabove deficiencies to a considerable extend. However the technologyfollowed in this system for maintaining the speed of the planet carrierand sun gear at the same level during normal drive, by directing thefluid discharge from the left side hydraulic pump rotating with theplanet carrier, to the suction side of the right side hydraulic pumprotating with the sun gear, can cause excessive heat during continuousoperation and can waste pressure energy to certain extent. The fluidunder pressure discharged from these pumps to the fluid tank during geardrive also wastes certain amount of pressure energy.

SUMMARY OF INVENTION

This invention discloses a transmission assembly which provides for anygear ratio right from zero to infinity, for forward and reverse movementas well, including the step up ratio for over drive, with an additionalprovision for higher ratio for building up higher torque for specialcircumstances, all in one configuration, resulting in better fuelefficiency, and better acceleration, at the same time reducing the useof hydraulic pumps to a large extent, and thus reducing the amount ofheat generated and wastage of pressure energy as well. This was madepossible in this system by incorporating an automatic gear couplingcontrolled by the microprocessor, which will connect the sun gear withplanet carrier and thus maintaining the speed of sun gear, planetcarrier and the ring gear at exactly the same level, during normaldrive, instead of directing the fluid discharge from left side (planetcarrier) pump to the input side of the right side (sun gear) pump as inthe previous invention. Also the fluid discharge from the right sidehydraulic pump, instead of directing into the fluid tank during geardrive, is diverted into a conventional hydraulic motor installed on theplanet carrier shaft in order to force the planet carrier to rotatefaster, and thus to accelerate the output gear of the planetary gearunit. The hydraulic motor can also be installed on the ring gear shaftfor better acceleration. The hydraulic motor can also be used fordriving the super charger, compressor, generator etc. if installedseparately. The present invention also provides a hand brake attached tothe second output shaft of the differential unit replacing the left sidehydraulic pump. By manually operating the hand brake, the speed of thesecond output shaft connected to the planet carrier can be brought downso that the direction of the rotation of the ring gear will change andthe vehicle will move in reverse direction. The present invention alsoincludes a flow control valve With variable orifice installed in thedischarge line of the right side (sun gear) hydraulic pump, which willbe automatically adjusted by the microprocessor to build up the fluidpressure for maintaining the required speed of the sun gear underdifferent modes of operation. This enables the fluid to always move in asingle direction and makes the circuit extremely simple, eliminating allthe complicated valves and controls in the previous invention. This canalso automatically adjust the vehicle speed in case of over load etc, asdecided by the microprocessor unit, during gear drive.

Another embodiment of the present invention includes a single stageplanetary gear unit where in the engine will be coupled to a commonshaft which is connected to the planet carrier, and also connected tothe ring gear through a conventional speed reduction unit, such as steelbelt with adjustable pulley, hydraulic torque converter, toroidal driveetc. The vehicle is connected to the sun gear.

In view of the above, the present invention is directed to an infinitelyvariable gear transmission system including a differential gear unit forinput, and a planetary gear unit with one hydraulic pump. In thepreferred embodiment the hydraulic circuit having a flow control valvewith variable orifice, intercouples the hydraulic pump, rotating withthe first output shaft of the differential gear unit and one of thethree gear elements of the planetary gear unit, and the second outputshaft rotating with the hydraulic motor and the second gear element, andincludes a controller operable to control the opening of the variableorifice, and precisely control the resistance exerted by the fluidpressure determining the speed of the third gear element.

Further scope of applicability of the present invention will becomeapparent from the following detailed description, claims, and drawings.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications with in the spirit and scope of the invention willbecome apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given here below, the appended claims, and theaccompanying drawings in which:

In sheet no. 1, FIG. 1 is the general assembly of the equipment, inaccordance with this invention, with the differential gear unit and theengine at the right end, the planetary gear unit at the left end, andthe automatic gear coupling with the hydraulic cylinder at the extremeleft end.

In sheet no. 2, FIG. 2 is the sectional view of the differential gearunit with the engine connected to the input of the differential unit,the planetary gear unit connected to the differential, the gear couplingfor connecting the sun gear and planet carrier, the hydraulic pumpconnected to the first out put shaft of the differential unit, thehydraulic motor connected to the planet carrier shaft, and the fluidlines connecting the hydraulic pump, hydraulic motor and the fluid tank.

In sheet no. 3, FIG. 3 is the sectional view of the planetary gear unitdirectly connected to the engine through the main drive shaft,eliminating the differential gear unit, the main drive shaft connectedto the ring gear through the conventional speed reduction unitconsisting of steel belt with adjustable pulleys, and the planet carrierconnected to the drive shaft through connecting gears, and the vehicleconnected to the sun gear.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The details of the differential gear unit, as shown in FIG. 2, includesthe second output shaft 1 with hand brake, the second output gear 2 forconnecting to the planet carrier of the planetary gear unit, the inputbevel gear 3, the engine 4 connected to the power input of thedifferential unit, the revolving pinion 5, differential body 6containing the revolving and rotating pinions, the output bevel gear 7,the first output gear 8 for connecting to the sun gear of the planetaryunit, the hydraulic pump 9 attached to the first output shaft of thedifferential unit, the flow control valve with variable orifice 10, theoutput bevel gear 11, the fluid line 12, the intermediate connectinggear 13 for coupling the first output gear to the sun gear, the planet14, the fluid discharge line 15, the hydraulic motor 16, the sun gear17, the connecting gear 18 attached to the sun gear, the connecting gear19 attached to the ring gear, the connecting gear 20 attached to theplanet carrier shaft, the planet carrier shaft 21, the planet carrier22, the ring gear 23, and the intermediate gear 24 for coupling thesecond output gear and planet carrier shaft, the coupling gears 25 and27 installed on the coupling shaft 26 for coupling the sun gear to theplanet carrier, the hydraulic unit 28 for actuating the coupling shaft,the fluid inlet and outlet lines 29 of the hydraulic unit.

The details of the planetary gear unit, as shown in FIG. 3, includes theconnecting gear 30 attached to the planet carrier shaft, the drivenpulley 31 of the speed reduction unit, the planet carrier shaft 32, theplanet carrier 33, the ring gear 34, the intermediate gear 35, theconnecting gear 36 fixed on the main drive shaft, the steel chain 37 ofthe speed reduction unit, the main drive shaft 38 connected to theengine, the driving pulley 39 of the speed reduction unit, the outputgear 40 of the planetary gear unit, the sun gear 41, the planet 42, andthe engine 43.

When the power from the prime mover (engine) is transmitted to thedifferential unit through the bevel gear pair, the output shafts of theunit start rotating. The rotation of the output shafts follows theformula 2N=N1+N2—Formula (1) where as N is the engine speed inrpm.(hereafter referred to as speed). N1 is the first output shaft speedand N2 is the second output shaft speed.

While the vehicle control lever is in the park position the hydraulicpump installed on the first output shaft sucks the fluid from the fluidtank and freely pumps the fluid back into the tank through the flowcontrol valve and the hydraulic motor installed on the planet carriershaft. Therefore the output shafts are free to rotate at any speed.

In the case of planetary gear if X1 is the speed of the sun gear, X2 isthe speed of planet carrier and X is the speed of ring gear(annulus)X1=4.5X2−3.5X—Formula (2). (The annulus is connected to the vehiclethrough the output gear) whereas (Z1+Z2)/Z1=4.5 and Z2/Z1=3.5; Z1=No. ofteeth on sun gear=24 and Z2=No. of teeth on annulus=84. Since the firstoutput is connected to the sun gear, and the second output shaft isconnected to the planet carrier N1=X1, and N2=X2.

If the engine speed is 1500 rpm, on applying formula (1) X1 will beequal to 2455 and X2 will be equal to 545. Similarly if the engine speedis 2000rpm, X1 will be equal to 3273 and X2 will be equal to 727. If theengine speed is 3000rpm, X1 will be 4909 and X2 will be 1091. In allthese cases applying the value of X1 and X2 in formula (2), the outputspeed of the planetary gear unit, i.e. the value of X will be zero;Normally in the neutral position the engine speed will be maintained at1,500 RPM and the speed of the hydraulic pump connected to the sun gearwill be at 2,455 RPM.

When the vehicle is accelerated the microprocessor control will comeinto action, and automatically adjust the variable orifice of the flowcontrol valve, to build up the fluid pressure to constantly maintain thesun gear speed at 2,454 RPM till the engine speed reaches 2,454 RPM forthe direct drive, other wise known as normal drive, the gear ratio being1:1. It may be noted from the formula—(2) that the tendency of the sungear will be always to move faster and the planet carrier to move slowerin order to slow down the ring gear connected to the vehicle. When theengine is accelerated, the sun gear speed will be always at 2,454; Butthe planet carrier speed will gradually increase with respect toFormula—(1).The resultant speed of the vehicle also will keep onincreasing according to Formula—(2).

The output speed of the vehicle, corresponding to 1500 to 2454rpm(engine speed) has been given below in Table—I.

Example: When engine speed is 2000 rpm, the R.S. output shaft speed is2454 rpm.Applying formula (1)

2N=N1+N2

2×2000=2454+N2

Therefore N2=1546

Applying formula (2)

X1=4.5X2−3.5X

X1=N1&X2=N2

Therefore 2454=4.5×1546−3.5X and X=1286=The vehicle speed.

TABLE I [RPM] Ring gear Engine First output Second output speed X speedN shaft speed X1 shaft speed X2 (vehicle speed) 1500 2454 546 0 15252454 596 65 1600 2454 746 258 1700 2454 946 515 1800 2454 1146 772 19002454 1346 1029 2000 2454 1546 1286 2454 2454 2454 2454The output speed is ranging from 0 to 2454, to provide enou startingtorque for the vehicle during the gear drive.

At 2454 rpm the microprocessor will actuate the hydraulic unit of theautomatic gear coupler, and connect the sun gear to the planet carrier.The coupler shaft will be axially moving so that the freely runningcoupling gear, will be engaged with the connecting gear coupled to thesun gear. The coupling gear at the other end of the shaft is alreadyengaged with the planet carrier through the connecting gear attached tothe planet carrier shaft. As seen from the Table (1) the engine, the sungear, the planet carrier and the ring gear will now be running at thesame speed for the normal drive as noted below.

X1=4.5X2−3.5X. Since X1=X2, X1=4.5X1−3.5X, Therefore X=X1; At the speedof 5250, the first and second output shafts, and also the planetary gearoutput will be at 5250. In this condition the vehicle is in directdrive.

If over drive is preferred at 5250 rpm (engine speed), themicroprocessor will again come into action by operating a manual switch,and automatically disconnect the gear coupling, and adjust the variableorifice of the flow control valve to control the fluid pressure toconstantly maintain the sun gear speed at 5,250 RPM, till the enginespeed reaches 6,000 RPM and the ring gear. speed 7,178 RPM. The speed ofthe sun gear, the planet carrier, the ring gear and the engine speed hasbeen given below. Please see (Table—II)

TABLE II [RPM] Engine First output Second output Ring gear speed N shaftspeed X1 shaft speed X2 speed X 5250 5250 5250 5250 5400 5250 5550 56355500 5250 5750 5892 5750 5250 6250 6536 5900 5250 6550 6921 6000 52506750 7178

As Example:

2N=N1+N2   (1)

2×6000=5250+N2

Therefore N2=6750

N1=X1& N2=X2

X1=4.5X2−3.5X   (2)

5250=4.5×6750−3.5X

Therefore X=7178 In this condition the vehicle is in over drive.

On return the vehicle speed will follow the same path till 5250 enginespeed. At 5,250 RPM the microprocessor will again come into action andactuate the gear coupling to connect sun gear with planet carrier sothat the vehicle will move in direct drive. At 2,454 speed, themicroprocessor will actuate the gear coupler and disconnect the sun gearfrom the planet carrier. The vehicle will then move in the gear drive asin table (1) given earlier. Here also there is an option to postpone theoperation of the automatic gear coupler so that the vehicle can continueto operate in direct drive if there is no over loading.

For the reverse drive the vehicle will be first brought to the neutralposition. The engine speed will be raised to 2,000 RPM. Therefore thespeed of X1 will be 3,273 RPM and X2 will be 727 RPM. By operating thehand brake fixed on the second output shaft, the speed of the secondoutput shaft of the differential gear unit connected to the planetcarrier can be reduced to approximately 500 RPM. Automatically the sungear speed will be increased to 3,500 RPM. From the formula (2) 4.5X2−X1=3.5 X Wherein X1=3,500 and X2=500 Therefore X will be equal to−357. The vehicle will now move in reverse and the gear ratio will be2000/357=5.6

In case higher starting torque is required, the engine speed has to beraised and the sun gear speed has to be maintained at a higher rate byadjusting the flow control valve as shown in the example given inTable—III below.

This drive is basically meant for high ranges. As example the enginespeed is raised to 3,208 RPM and the sun gear speed is set at 5,250 RPMby the microprocessor. The torque at 3,250 engine speed will be3,250/107=30.37At 4000 engine speedApplying formula (1) 2N=N1+N2

Therefore 2×4000=5250+N2 Therefore N2=2750

X1=4.5X2−3.5X   Applying formula (2)

N1=X1& N2=X2

Therefore 5250=4.5×2750−3.5X Therefore X=2035

TABLE III [RPM] Engine First output Second output Ring gear speed Nshaft speed XI shaft speed X2 speed X 3208 5250 1166 0 3250 5250 1250107 3500 5250 1750 750 4000 5250 2750 2035 4500 5250 3750 3321 5000 52504750 4607 5250 5250 5250 5250

When the vehicle is in the neutral position and if the sun gear speedhas been already set by the microprocessor at 2,454 RPM, the sun gearspeed X1 can not increase. Therefore the vehicle can not move backwardeven when the vehicle is kept idling in the neutral position, on anupward inclination. This can avoid a few accidents caused by thevehicles moving backward and hitting the vehicle behind at the trafficpoints. Please see the formula—(2) 4.5 X2−X1=3.5 X The vehicle can movebackwards only if the value of X1 increases.

The hand brake installed on the second output shaft, if actuated, canstop the vehicle faster in the event of an emergency. A valve installedin the fluid return line which can be automatically closed by themicroprocessor, can also stop the vehicle quickly during an emergency,provided the vehicle is in gear drive.

In another embodiment the engine is connected to a common shaft which isdirectly connected to the planet carrier and also connected to the ringgear through a conventional speed varying mechanism, such as steel beltwith adjustable pulley, the hydraulic torque convertor, the toroidaldrive system etc. where in the differential gear unit and the hydraulicpump, and the hydraulic circuitry with the flow control valve etc can betotally eliminated. The vehicle in this case is connected to the sungear. This will make the system much simpler, lighter, and the initialcost also can be reduced. However the deficiency of the system is thedelayed response to the load change, the limitation to the max. load tobe transmitted, and comparatively lower transmission efficiency. Forreverse movement the conventional gear unit has to be used. In order tolimit the ratio of the speed variation, the planetary gear unit havingsmaller diameter has to be selected in this case. Therefore instead of4.5 and 3.5 ratio in the previous embodiment, in this embodiment theratio of 3 and 2 has been chosen. This means Z2/Z1=2 and (Z1+Z2)/Z1=3.In this case the no. of teeth on sun gear and ring gear will berespectively 24 and 48.The vehicle has to be connected to the sun gear.The formula will be

X1=3X2−2X. In this case since the max. torque has to be transmitted bythe sun gear having smaller diameter, the surface stress on the gearteeth could be quite high.Please see Table—IV below for the vehicle speed etc.

TABLE IV [RPM]{grave over ( )} Planet carrier Ring gear Sun gear gearratio speed X2 speed X speed X1 X2/X1 1500 2250 0 0 1600 2154 492 3.251700 2266 567 3.00 1800 2372 655 2.75 1900 2470 760 2.50 2000 2555 8892.25 2200 2672 1257 1.75 2400 2640 1920 1.25 2500 2500 2500 1.00

During the entire operation the microprocessor will continuously receivethe data on the throttle position, the suction pressure of the engine,the engine temperature, the lubrication oil temperature and the enginespeed through sensors. If the engine speed and the suction pressurematches with the throttle position, and the temperature is steady, theindication is that the engine produces enough torque required for thetraction. At the moment there is an adverse change in any of theconditions, the microprocessor will immediately adjust the throttleposition and bring down the engine speed to build up better torque.Similarly at any time during the gear drive, the driver can choose anygear ratio of his choice by manually operating the flow control valve.

The idle speed range and the speed limit settings of the differentialgear output shafts can be selected depending on the type of vehicle andthe users preference. The entire drive transmission can be controlled bya 32 bit 40 MHz microprocessor.

The foregoing discussion discloses and describes the exemplaryembodiment of the present invention. One skilled in the art will readilyrecognize from such discussion, and from the accompanying drawings andclaims that various changes, modifications and variations can be madetherein without departing from the true spirit and fair scope of theinvention as defined by the following claims.

1. An infinitely variable gear transmission system comprising: adifferential gear unit coupled to a power input from a prime mover of avehicle; a hydraulic pump, a single stage planetary gear unit drivablyintercoupling a sun gear with a first output shaft of said differentialgear unit, and a planet carrier with a second output shaft, saidplanetary gear unit including the sun gear, a ring gear, the planetcarrier, and at least one planet gear mounted on said planet carrier torotate with and relative to said planet carrier and meshed with the sungear and ring gear; wherein, a hydraulic circuit having a flow controlvalve with variable orifice, hydraulically intercoupling the hydraulicpump coupled to the first output shaft of said differential gear unit,and a control unit selectively controlling the resistance exerted by thefluid pressure on sun gear to control the speed of the ring gear of saidplanetary gear unit coupled to a drive shaft of the vehicle, in bothclockwise and anticlockwise direction, to provide the desired speed,during forward, reverse and over drive.
 2. The infinitely variable geartransmission system of claim 1 wherein said hydraulic circuit includes ahydraulic motor coupled to the planet carrier shaft, hydraulicallyintercoupling the hydraulic pump and the flow control valve withvariable orifice, to improve the speed of planet carrier to acceleratethe ring gear connected to the vehicle.
 3. The infinitely variable geartransmission of claim 1 includes an automatic gear coupling to beactuated by the microprocessor to couple the sun gear and planet carrierin order to maintain the speed of sun gear, planet carrier, ring gearand the prime mover at the same level during normal drive.
 4. Theinfinitely variable gear transmission of claim 1 includes a manuallyoperated hand brake coupled to the second output shaft of thedifferential gear unit to reduce the speed of the planet carrier inorder to reverse the direction of rotation of the ring gear connected tothe vehicle and also to stop the vehicle quickly on an emergency.
 5. Themicroprocessor control system of claim 3 continuously monitors theaccelerator pedal position, the engine speed, the suction speed, theengine temperature and the lubrication oil temperature, to adjust theengine throttle to reduce the vehicle speed in case of overloading. 6.The microprocessor control unit in claim 3 sets the speed of the sungear at constant level when the vehicle is idling in neutral and thusprevent the accidental movement of the vehicle in the reverse direction.7. The infinitely variable gear transmission system of claim 1 includesa microprocessor unit and a planetary gear unit, having its planetcarrier directly coupled to the prime mover, and the ring gear coupledto the prime mover through a conventional speed variator, such as steelchain with adjustable pulley, hydraulic torque convertor, toroidal driveetc. to adjust the speed of the sun gear connected to the vehicle byautomatically adjusting the speed variator.
 8. The flow control valvewith variable orifice in claim 3 sets the functional speed of the sungear at a higher level as desired by the microprocessor control unit toreduce the speed of ring gear to build up additional torque duringspecial situations.
 9. The infinitely variable gear transmission systemof claim 1 includes a manual switch which delays the action of automaticgear coupling to detach the sun gear and planet carrier for gear drive,in order to keep the vehicle running in normal drive during specialsituations.
 10. The infinitely variable gear transmission system ofclaim 2 wherein said hydraulic circuit includes a hydraulic motorcoupled to the ring gear shaft instead of the planet carrier shaft,hydraulically intercoupling the hydraulic pump and the flow controlvalve with variable orifice, to accelerate the ring gear connected tothe vehicle.